102 



Messrs. F. L. Usher and J. H. Priestley. [Apr. 13, 



wholly so in the case of hydrogen peroxide, it was thought advisable to 

 supplement it by further experiments. 



1. The Products of Photolysis of Aqueous Carbon Dioxide. 

 (a) In Vitro. — No further experiments have been made with solutions of 

 uranium salts ; either no sensitiser at all, or chlorophyll films, as described in 

 Part II, have been employed. It has been found possible to decompose an 

 aqueous solution of carbon dioxide without either an optical sensitiser or a 

 reducing agent, by supplying it with energy in two different ways, viz. : 

 (1) By bombarding it with «- and /3-rays from radium emanation and its 

 products, and (2) by exposing it to the light emitted by a quartz mercury- 

 vapour lamp. 



The experiment with «- and ft- rays was carried out as follows : — About 

 200 c.c. of distilled water were saturated with carbon dioxide, and into 

 this solution about 0"0001 c.c. of radium emanation was introduced. 

 After four weeks the solution was tested for formaldehyde by Schryver's 

 method.* It contained an appreciable quantity of formaldehyde, a well- 

 marked red colour being observed when the test was applied. The greater 

 part of the aldehyde was in a polymerised form, but no sugar was detected. 

 Another portion of the liquid gave a yellow coloration with a solution of 

 titanium oxide in sulphuric acid, showing the presence of hydrogen peroxide. 



The recently published investigations of Kernbaum on the action of 

 /3-raysf and of ultra-violet lightj on water, in which the author stated that 

 hydrogen and hydrogen peroxide were simultaneously produced, suggested an 

 examination of the action of ultra-violet bight on solutions of carbon dioxide. 

 In a preliminary experiment, a shallow glass dish containing distilled water was 

 placed immediately beneath, and 2 to 3 cms. from, a quartz mercury-vapour 

 lamp, and carbon dioxide was bubbled through the water while the lamp was 

 in action. After two hours' illumination the water contained hydrogen 

 peroxide, which was identified by the titanium sulphate reaction, as well as a 

 small quantity of formaldehyde. A blank experiment, without carbon 

 dioxide, was then carried out for the same length of time, but in this case 

 formaldehyde was again detected, in addition to hydrogen peroxide. This 

 may have been due to the presence of atmospheric carbon dioxide, but since 

 it was possible that the formaldehyde might have been formed as a decom- 

 position-product of dust particles from the air or the water, the experiment 

 was repeated with greater precautions. 



* 1 Eoy. Soc. Proc.,' B, vol. 82, p. 226. 



t ' Comptes Kendus,' 1909, vol. 148, p. 705. 



\ Ibid., 1909, vol. 149, p. 273. 



